The goal of this research is to contribute to an understanding of the structural and functional organization of the eukaryotic chromosome, especially in relation to the process of DNA replication, using Saccharomyces cerevisiae, a lower eukaryotic, as a model system. We are studying sequences whose transformation properties suggest that they function as origins of replication. We are investigating cell cycle control over their replication and the segregation patterns of plasmids containing such sequences. We are also studying the replication properties of heterologous DNAs both in yeast and after their re-introduction into a homologous cell. Finally, we are isolating genes required for both initiation and elongation of yeast DNA replication in order to learn more about the role of such genes in DNA synthesis.